We analyzed baseline data from the first 255 patients, who participated in a community-based cohort study, CARDIPP (Cardiovascular Risk factors in Patients with Diabetes – a Prospective study in Primary care). CARDIPP was launched in November 2005 and completed in 2008 with the aim to identify markers of cardiovascular disease to facilitate earlier and individually adjusted intervention, in middle aged men and women with type 2 diabetes. CARDIPP comprises data on an extended annual follow up on patients with type 2 diabetes, aged 55–66 years, consecutively recruited from 25 different primary health care centers in the counties of Östergötland and Jönköping, Sweden. All patients with type 2 diabetes, aged 55–66 years, who attended an annual follow-up at the health care centers, were consecutively invited to participate in the study. Detailed information about the structure and results from CARDIPP has been described previously [17, 18]. The centres were located in different demographic areas and differed in size. However, the model of treatment and care of type 2 diabetes was organized similarly and all primary care centres adhered to the same national guidelines of diabetes care.
Nurses especially dedicated to treatment of diabetes at the primary health care centers, measured height (to the nearest cm) and weight (to the nearest 0.1 kg) with the patients wearing light indoor clothing. Waist circumference (WC) was measured according to WHO’s recommendations with the patient standing, after a regular expiration, to the nearest cm, midway between the lowest rib and the iliac crest. SAD was recorded with the patient in the supine position and with bent knees, with a standardized sliding beam calliper at the highest point of the abdomen.
A standardized medical history was taken, including data on diabetes duration and ongoing medication.
Blood specimens were drawn in the morning after a 10 hour over night fast. Routine tests such as HbA1c, plasma glucose and serum lipids were analysed according to routines at the primary health care centres. Levels of cholesterol, HDL and triglycerides was measured with enzymatic methodology and spectrophotometry, Selectra E,Vital Scientefic, Netherlands/Triolab. LDL was calculated by Friedewalds formula: LDL = cholesterol - HDL - 0.45 × fS/P-triglycerides.
HbA1c was analysed according to the Swedish Mono-S HPLC. In this study, all HbA1c values were converted to DCCT standard values using the formula: HbA1c DCCT = 0.923 × HbA1c (Mono-S) + 1.345 (R2 = 0.998)  and data on HbA1c is also reported in IFCC units. Blood samples were frozen for later analysis of CRP, apolipoprotein B (apoB) and apolipoprotein A-I (apoA-I) at the Centre for Laboratory medicine, Linköping University Hospital, Linköping, Sweden. Levels of apoB and apoA-I were measured by immunoturbidimetric assays, Advia 1800, DakoCytomation, Glostrup, Denmark. Coefficient of variation (CV) for apoB was 1.2% CV for apoA-I was 1.8%. CRP was also measured by immunoturbidimetric assays, Advia 1800, Siemens Diagnostic Medical Solutions, Erlangen, Germany. The detection level was 0.12 mg/L and CV was 1.6%. CRP values above 10mg/ml were excluded from the analyses according to current guidelines .
Physiological vascular examinations
The blood pressure measurements, carotid ultrasonographic investigations, PWV and SAD were performed at the Department of Physiology, Linköping University Hospital, Linköping, Sweden and at the County Hospital Ryhov, Jönköping, Sweden. Systolic blood pressure (SBP) was measured with oscillometric technique (Dinamap PRO 200 Monitor, Critikon, Tampa, FL, USA) on the same occasion as the clinic physiological investigations. After at least 10 minutes rest in supine position, using an appropriately sized cuff, the BP was recorded in both arms. The mean value of two measurements in the arm with the highest systolic BP was used in further analyses in the study. IMT of the carotid arteries were evaluated using a B-mode ultrasound. A digital ultrasound system (ATL HDI 5000, Bothell, WA, USA) equipped with a broadband linear transducer (L12-5) was used for scanning the carotid artery in longitudinal section. ECG leads were connected. For lumen diameter (LD) and IMT determination, during diastole, three consecutive frozen images with special focus on lumen-intima echo and media-adventitia echo of the far arterial wall were saved for later analysis. The digital B-mode images were subsequently transferred to a PC, where software for off-line measurement of LD and IMT is installed (Artery Measurement System II, Image and Data Analysis, Gothenburg, Sweden). Calibration and subsequent measurement was performed by manually tracing a cursor along the leading edge of the intima-lumen echo of the near wall, leading edge of the lumen- intima echo and media-adventitia echo of the far wall. A 10 mm long section of the common carotid artery in the proximity of the carotid bulb was selected to obtain mean LD and far wall IMT. During analysis, the measurement window was hidden for the reader and values were saved in a text file. Mean values of IMT and carotid LD from both the right and the left sides were used in all analyses. Aortic PWV was measured with applanation tonometry (SphygmoCor® system, model MM3, AtCor Medical, Sydney, Australia) over the carotid and femoral arteries. The aortic pulse wave transit times were measured by electrocardiogram-guided readings of the femoral arterial pulse waves, using the carotid arterial pulse wave as the reference site. The surface distances were estimated from the suprasternal notch to the carotid and femoral measurement sites, respectively. PWV was calculated by dividing the surface distance with the pulse wave transit time yielding m × s-1.
The CARDIPP-R comprises a re-investigation of the cohort four years after the completion of the baseline examination. In CARDIPP-R, all participants from the baseline study were invited to the re-investigation that was conducted at the Department of Physiology, Linköping University Hospital and at County Hospital Ryhov, Jönköping, Sweden. This study population comprises subjects with type 2 diabetes who were subjected to the baseline examination in 2006 and underwent the subsequent re-investigation in 2010.
The CARDIPP-R study protocol for the blood pressure measurements, the carotid ultrasonographic investigations and tonometry for measurements of the carotid, femoral and radial pulse pressure wave form and pulse wave velocity followed identical manual as in the baseline investigation. The routine laboratory tests were performed at the different health-care centers as described in the baseline protocol. In the follow-up investigation, CRP was not measured with an identical method as at baseline, thus our results regarding CRP values are confined to baseline data only.
IBM SPSS statistics 19 (IBM corporation, Somers, NY, USA) was used for statistical analyses. CRP, was log transformed due to skewed distribution. Pearson correlation coefficients were calculated between the different measurements, using bivariate correlation analysis. Statistical significance was assumed when p < 0.05. In multiple linear regression analyses with IMT or PWV, as dependent variables, the increase of one unit for each of the variables explored, confered a change in IMT or PWV respectively expressed as the regression coefficient (beta) with 95 percent confidence intervals (CI). In stepwise linear regression criteria for entry were p < 0.05 and for removal p > 0.1.
All participants gave written informed consent prior to participating in the study. The study, which complied with the declaration of Helsinki, was approved by the Regional Ethical Review Board in Linköping, Sweden.